This invention concerns a method for the production of an eyeglass frame from a mololithic plastic workpiece, and further relates to a holding apparatus useful in said method.
A widely used style of eyeglass frame is one vehicle the entire perimeter of each lens engages a rim which defines a holding aperture that completely surrounds the lens, said rims being disposed in substantially coplanar relationship and interconnected by a nosepiece portion representing a continuous integral extension of the rims. The frame is generally fabricated of plastic material. A pair of elongated arms adapted to engage the ears of the user are generally pivotably attached to the opposite extremities of the frame.
It has generally been found that although such frames can be made by injection molding, equipment costs are extremely high, particularly for mold design. Accordingly, injection molding methods are not utilized unless a high volume run of a single type and size frame is contemplated. Alternatively, frames can be made by a milling operation. The units costs in the milling method are higher than the molding method because of the considerable time required per frame, but the equipment costs are much lower and the versatility is significantly greater.
The milling method of frame-making is generally conducted upon a flat starting blank such as a slab of cellulose acetate. Techniques and equipment heretofore disclosed for speeding the milling operation have compromised the quality of the resultant frame product. A primary aspect of the milling operation involves the precision securement of the workpiece within a holder device which facilitates accurate milling.
It is accordingly an object of the present invention to provide a holder apparatus for rapidly engaging a plastic slab workpiece, holding the workpiece accurately during a milling operation which forms the workpiece into an eyeglass frame, and rapidly releasing said frame.
It is another object of this invention to provide a holder as in the foregoing object useful in producing eyeglass frames of varied size and shape.
It is a further object of the present invention to provide a method for producing an eyeglass frame from a plastic workpiece utilizing apparatus of the aforesaid general nature.
These objects and other objects and advantages of the invention will be apparent from the following description.